International Concrete Abstracts Portal

SP-162 This fact filled symposium, developed in honor of Mete A Sozen, contains 17 highly informative papers. A spectacular addition to all reference shelves. This symposium took place at the ACI Fall convention in Tarpon Springs, Florida in October of 1994. The Sozen Symposium consisted of three sessions with eighteen speakers. The symposium and this SP volume were organized to permit Mete's students and colleagues to honor and thank him for his council and guidance during their studies at the University of Illinois.

Design algorithms expressed in current building codes and practiced in design offices focus attention on earthquake induced lateral forces and away from earthquake induced lateral displacements. These procedures have led to development of structural systems in which a portion of the structural frame is designed to resist the total seismic design force, while a substantial remainder of the structure is proportioned assuming it resists only gravity loads. This approach is commonly applied to design of slab-column systems in regions of high seismicity. For such systems, a displacement-oriented approach has advantages. Applications of the approach are described.

The objective of this paper is to present models for the design of confined masonry structures based on the available experimental data. In particular, this study deals with in-plane response of masonry walls subjected to lateral forces, with emphasis on aspects of initial stiffness, strength, and deformation capacity. The experimental information used in this work comprises tests performed at the Structures Laboratory of the Catholic University of Peru. Results indicate that stiffness can be calculated considering a wall cross section inertia using the transformed cross section concept with the appropriate moduli of elasticity for concrete and masonry. Bending strength can be estimated reasonably well, assuming for the cross section (1) a rectangular compressive stress distribution, (2) zero strength under tension, and (3) a linear strain distribution. Unit shear strength could be safely calculated as 0.5 f'm, where f'm is the characteristic compressive strength of masonry. It is observed that confined masonry can develop drift values larger than 0.5 percent of wall height, which is comparable to that of reinforced masonry. Deformation capacity is observed to increase for increasing wall horizontal reinforcement ratio and column horizontal and vertical reinforcement and to be reduced with increasing axial load.

Force-deformation relationship of high-strength reinforced concrete beam members observed in the laboratory test was idealized by a trilinear relation for use in a nonlinear earthquake response analysis. Methods to evaluate the relationship were examined and the reliability of the methods were discussed with respect to the observed relations. Calculated initial stiffness is shown to significantly underestimate the observed value; a large coefficient of variation was attributed to accidental and shrinkage cracking in the specimen prior to the test. A similar large coefficient of variation was observed in the evaluation of cracking moment. Yield and ultimate moments could be favorably estimated by the theory. An empirical formula was proposed to evaluate yield deformation. An importance of controlling the elastic modulus of concrete in construction is emphasized if a structure is expected to behave as designed during an earthquake.

Objective evaluation of structural damage in buildings which have been subjected to strong ground motions is an undertaking in which expert knowledge and the ability to process correlated but fuzzy information in a consistent way must be blended. Often, in the immediate aftermath of earthquakes, field data is collected by survey teams whose expertise is variable. The use of knowledge-based systems capable of reaching an unequivocal decision on the damage state of a given building on the basis of queries arranged in a consistent hierarchical order would remove human subjectivity. This paper describes the internal design of an expert system called EPEDA, which is used as a tool for making a numerical ranking of damage in reinforced concrete buildings. Damage to individual elements is quantified on the basis of severity, relative member importance, and number of affected elements. Factors contributory in nature to the damage are summed with this score, as are scores expressing the overall system vulnerability. The final score is expressed as a number ranging from zero to 100. An example case is worked out to illustrate how the system works.